Preparation of 2-(pyridyl)ethyl bis-(trialkyl silyl)phosphonate derivatives substituted phosphorous compounds

ABSTRACT

A process for producing phosphonate esters containing the 2-(pyridyl)ethyl group by reacting a vinylpyridine with a di- or trihydrocarbylphosphite in the presence of a selected silane, protic acid, or Lewis acid is disclosed. Also disclosed are novel silylphosphonate esters containing the 2-(pyridyl)ethyl group. All of the compounds produced herein are useful as catalysts for increasing the molecular weight of polyamides.

This is a division of application Ser. No. 07/649,542, filed Jan. 24,1991, now U.S. Pat. No. 5,194,616.

FIELD OF INVENTION

A process for the preparation of 2-(pyridyl)ethyl substitutedphosphorous compounds, by contacting a vinylpyridine and a phosphorouscompound in the presence of a silicon halide, a protic acid, or aselected Lewis acid. Also provided are novel 2-(pyridyl)ethyl(bis)silylphosphonates and their use as catalysts in increasing themolecular weight of polyamides.

BACKGROUND OF THE INVENTION

The reaction of dihydrocarbylphosphites with a variety of olefinicunsaturated organic compounds, so that a phosphorous-carbon bond isformed, is known in the art, see for background for example: X. Lu andJ. Zhu, Synthesis, p. 563-564 (1986); G. Optiz, et. al., Ann., vol. 665,p. 91-101 (1963); I. Tyurenkov, et. al., Khim. Farm. Zh., vol. 22, p.170-174 (1988); V. Shchepin, et. al., Zh. Obshch. Khim., vol. 57, p.2144 (1987); and V. Ovchinnikov, et. al., Zh. Obshch. Khim., vol. 54, p.1916-1917 (1984). None of these disclose the use of vinylpyridines insuch reactions.

E. Maruszewska-Wieczorkowska and J. Michalski, J. Org. Chem., vol. 23,p. 1886-1889 (1958) report the synthesis of various2-(pyridyl)phosphonates by the reaction of a vinylpyridine with adialkyl phosphite, optionally with a sodium ethoxide catalyst. Withoutthe catalyst, it was reported that yields were lower, and considerableamounts of polymeric substances were formed. Sodium ethoxide, thecatalyst used by these authors, is a base, and no mention is made of theuse of halogen containing or acidic catalysts, as used herein.

E. Boyd, et. al., Tet. Lett., vol. 31, p. 2933-2936 (1990), report thereaction of triethylammonium phosphinate, trimethylchlorosilane, andalpha,beta-unsaturated ester (such as an acrylate) resulted in theformation of (beta-ester)alkyl substituted phosphonic acid.Bis(trimethylsilyl)phosphinite was postulated as an intermediate.However, only alpha-beta unsaturated esters are reported to be suitablereactants.

Similarly, J. K. Thottahil, et. al., Tet. Lett., vol. 25, p. 4741-4744(1984), reports that phosphonous esters in the presence oftrimethylchlorosilane, and triethylamine react with substrates suitablefor Michael addition type reactions (i.e., alpha, beta unsaturatedesters and aldehydes) to give various addition products to thephosphonous ester. Depending on the reactants, 1,2 or 1,4 addition wasobtained. N,O-Bis(trimethylsilyl)acetamide could be used in place oftrimethylchlorosilane. No mention is made in this paper of using amines,such as a vinylpyridine, as substrates.

M-P. Teulade and P. Savignac, Synthesis-Stutt., vol. 11, p. 1037-1039(1987) report the reaction of triethyl phosphite with alpha-betaunsaturated aldimines catalyzed by formic acid. No mention is made ofusing vinylpyridines as reactants.

U.S. Pat. No. 4,912,175 describes the use of 2-(pyridyl)ethyl phosphonicesters and acids as catalysts for increasing the molecular weight ofpolyamides such as nylon 6,6. No mention is made of the use of silylesters as such catalysts.

It is the object of this invention to provide a convenient, high yieldand economic synthesis of 2-(pyridyl)ethyl substituted phosphonateesters, which are useful catalysts for increasing the molecular weightof polyamides. Another objective is to provide novel 2-(pyridyl)ethylsubstituted bis(silyl)phosphonate esters that are also useful ascatalysts for increasing the molecular weight of polyamides.

SUMMARY OF THE INVENTION

This invention concerns a process for the production of 2-(pyridyl)ethylsubstituted phosphorous compounds, comprising, contacting (1) a firstcompound selected from the group consisting of P(OR¹)₃ and HP(O)(OR¹)₂,wherein each R¹ is independently alkyl, substituted alkyl, silyl, orsubstituted silyl with (2) a vinylpyridine, and (3) a third compoundselected from the group consisting of

(a) a silane of the formula R² _(n) SiX_(4-n) wherein each R² isindependently hydrocarbyl or substituted hydrocarbyl, each X isindependently chlorine, bromine, or an oxyanion whose conjugate acid hasa pKa, when measured in water, of less than about 2, and n is 0, 1, 2,or 3;

(b) a protic acid of the formula HPY wherein Y is an anion and p is thevalence of Y, provided said protic acid has a pKa of about 6 or less inwater; and

(c) a Lewis acid of the formula MZ_(q), wherein M is a metal ormetalloid atom, Z is hydrocarbyl, chlorine or bromine, and q is thevalence of M;

and provided that when said third compound is (a) or (c) said firstcompound is HP(O)(OR¹)₂, and further provided that when said thirdcompound is (b) said first compound is P(OR¹)₃.

This invention also concerns a compound of the formula ##STR1## whereineach R³ is independently hydrocarbyl or substituted hydrocarbyl.

This invention also concerns a process for increasing the molecularweight of a polyamide comprising heating a polyamide in the presence ofa compound of the formula ##STR2## wherein each R² is independentlyhydrocarbyl or substituted hydrocarbyl.

DETAILED DESCRIPTION OF THE INVENTION

This invention concerns a method of producing 2-(pyridyl)ethylsubstituted phosphorous compounds of the general type ##STR3## Specificcompounds and their uses are also claimed. The 2-(pyridyl)ethyl group isderived (in synthesis) from a vinylpyridine of the structure ##STR4##The ring carbon atoms of the pyridine ring may be substituted withgroups that do not interfere with the reactions herein, such as alkyland alkoxy. Preferred vinylpyridine compounds herein for all processesand compounds (and their corresponding groups when bound to phosphorous)are 2-vinylpyridine [2-(2-pyridyl)ethyl] and 4-vinylpyridine[2-(4-pyridyl)ethyl]. An especially preferred vinylpyridine compoundherein for all processes and compounds (and its corresponding group whenbound to phosphorous) is 2-vinylpyridine[2-(2-pyridyl)ethyl].

In the process for producing 2-(pyridyl)ethyl containing phosphorouscompounds, it is preferred if each R¹ is independently n-alkylcontaining up to about 6 carbon atoms, and especially preferred if R¹ ismethyl or ethyl. By substituted alkyl or substituted silyl are meantalkyl or silyl groups substituted with groups that do not interfere withthe reaction. Suitable groups include, but are not limited to, phenyl,p-chlorophenyl, ether, ester, alkyl, fluoro, and nitrile.

In the process for producing 2-(pyridyl)ethyl containing phosphorouscompounds, it is preferred that in the silane, X is chlorine or bromine,and in an especially preferred silane, X is chlorine. A contemplatedequivalent for X is iodine. By an oxyanion for X, is meant an anionwherein the negative charge is formally on an oxygen atom. It is alsopreferred if each R² is independently an alkyl group or phenyl, morepreferred if each R² is independently a normal alkyl group containing upto 4 carbon atoms or phenyl, and most preferred if R² is methyl. It ispreferred if n is 0 or 2, or 3, and most preferred if n is 3.

Suitable silanes include, but are not limited to, silicon tetrachloride,methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane,trimethylbromosilane, silicon tetrabromide, trimethylsilyltrifluoromethylsulfonate, trimethylsilyl trifluoroacetate,phenylmethyldichlorosilane, phenyltrchlorosilane, triphenylchlorosilane,diphenyldichlorosilane, t-butyltrichlorosilane,n-octadecyltrichlorosilane, andalpha-naphthyl-p-chlorophenyldichlorosilane. Preferred silanes aretrimethylchlorosilane, trimethylsilyl trifluoromethylsulfonate,trimethylsilyl trifluoroacetate, trimethylbromosilane,dimethyldichlorosilane, and silicon tetrachloride. Especially preferredsilanes are dimethyldichlorosilane, and trimethylchlorosilane.

The silane may be present in catalytically effective amounts, or greaterthan catalytic amounts, and the product obtained depends upon the amountused. Any catalytically effective amount of silane may be used, and ithas been found that about 0.1 (or more) equivalents of the X group permole of vinylpyridine or starting phosphorous compound is catalyticallyeffective. For one mole of vinylpyridine or phosphorous compound, about0.1 moles (or more) of trimethylchlorosilane, or 0.025 moles of silicontetrachloride would be used. Up to about one equivalent of X group theprincipal desired product obtained has the structure ##STR5## but aboveabout 2.2 equivalents of X, increasing amounts of the structure ##STR6##are obtained. At about 3 equivalents of X per mole of vinylpyridine orphosphorous compound, the product consists almost entirely of the latterstructure. In the latter case, it will be understood by those skilled inthe art, that when there is more than one X group present in the silane,the product may be a complex mixture of oligomers, with some siliconatoms being bound (through oxygen) to more than one phosphorous atom. Itis preferred, if more than one equivalent of X group is used, that n inthe silane formula be 3. More than 3 equivalents of X group may be used,but it accomplishes nothing advantageous.

When the silane is used, no temperature limitations except those relatedto starting material and product stability are known, but in order toachieve convenient reaction rates, it is preferred to run the process,if more than about 2.2 equivalents of X per mole of vinylpyridine orphosphorous compound is used, from about 20° C. to about 130° C.,preferably about 50° C. to about 130° C., and more preferably about 70°C. to about 120° C., and if less than about 2.2 equivalents of X permole of vinylpyridine or phosphorous compound are used, from about 0° C.to about 130° C., preferably about 15° C. to about 50° C., and morepreferably about 20° C. to about 30° C. The reaction may be run neat orin a solvent, but neat is preferred if less than about one equivalent ofX for each mole of vinylpyridine or phosphorous compound is present inthe process. Suitable solvents are aprotic solvents that don't reactwith the silane or other ingredients or products, such as acetonitrile,methylene chloride and toluene. The process may be run in any vessel notaffected by the reactants or products, such as glass. Using lowerboiling ingredients at higher temperatures may require the use of apressure vessel, at autogenous pressure.

When the silane is used, is it preferred to exclude water and oxygen,since these may react with the starting materials or products. Smallamounts of these may be tolerated, but use up some of the reagents. Itis convenient to run the reaction under an inert atmosphere, such asnitrogen or argon. Vigorous agitation is preferred to assure mixing ofthe reactants. The product may be isolated by distillation, of if highboiling, by evaporation of solvent and byproducts. If oligomers arepresent because the silane had more than one X group on each siliconatom (n<3), then it may be more convenient to hydrolyze the product tothe corresponding phosphonic acid, if that is the desired or useableproduct. With any of the third compounds present, if the phosphonic acidis the desired product, the reaction mixture may be hydrolyzed in afurther step to the acid. The phosphonic acids are also useful ascatalysts for increasing the molecular weight of polyamides. Suchhydrolyses are known to those skilled in the art, for example E.Maruszewska-Wieczorkowska, supra, which is hereby included by reference.

When any of the third compounds is present, the ratio of vinylpyridineto phosphorous compound is not critical, but an approximately 1:1 molarratio is desirable, since this results in the most efficient use of thestarting materials.

The third compound may be a protic acid whose pKa when measured in wateris less than about 6. If water cannot be used to measure the pKa, thenthe pKa may be measured in dimethylsulfoxide, and compared with similarcompounds whose pKa in water is known. Some preferred acids have a pKaof about 1 or less. Preferred protic acids are carboxylic acids andmineral acids. These include, but are not limited to, hydrochloric acid,hydrobromic acid, phosphorous acid, sulfuric acid, formic acid, aceticacid, benzoic acid, trifluoromethanesulfonic acid, trifluoroacetic acid,chloroacetic acid, and isobutyric acid. Preferred acids are hydrochloricacid, hydrobromic acid, formic acid, trifluoroacetic acid, and aceticacid.

When a protic acid is used, the ingredients may be added in any order,but it may be convenient to first combine the protic acid and thevinylpyridine to form the vinylpyridine salt, such as the vinylpyridinehydrochloride. This reaction is exothermic. The salt may be isolated andadded as a "pure" compound. Although not critical, it is preferred ifthe molar ratio of protic acid to vinyl pyridine is about 1. Loweryields will result if this ratio is less than 1, and adding more proticacid is believed not to improve the reaction.

When the protic acid is used, no temperature limitations except thoserelated to starting material and product stability are known, but inorder to achieve convenient reaction rates, it is preferred to run theprocess from about 0° C. to about 130° C., preferably about 15° C. toabout 50° C., and more preferably about 20° C. to about 30° C. Thereaction may be run neat or in a solvent, but a solvent is preferred.Suitable solvents are aprotic solvents that don't react with theingredients or products, such as acetonitrile, methylene chloride andtoluene. The reaction may be run in any vessel not affected by thereactants or products, such as glass.

When a protic acid is used, is it preferred to exclude water and oxygen,since these may react with the starting materials or products. Smallamounts may be tolerated, but use up some of the reagents. It isconvenient to run the reaction under an inert atmosphere, such asnitrogen or argon. Vigorous agitation is preferred to assure mixing ofthe reactants. The product may be isolated by distillation, or if highboiling, by evaporation of solvent and byproducts. A byproduct of thereaction with the protic acid is the compound R¹ Y. For example if theprotic acid is hydrochloric acid and R¹ is ethyl, the byproduct will beethyl chloride. Provision should be made to remove this byproduct,particularly if it is low boiling.

The process may also be carried out in the presence of a third compoundwhich is a Lewis acid. Useful Lewis acids, include, but are not limitedto, TiCl₄, AlCl₃, AlBr₃, SnCl₄, BCl₃, BBr₃, and triphenylboron.Preferred Lewis acids are TiCl₄, SnCl₁₄ and AlCl₃. Contemplatedequivalents for Z are fluorine and iodine. A catalytically effectiveamount of the Lewis acid should be used, preferably at least about 0.05mole of Lewis acid per mole of vinylpyridine, and more preferably about0.1 to about 0.2 mole of Lewis acid per mole of vinylpyridine.

When the Lewis acid is used, no temperature limitations except thoserelated to starting material and product stability are known, but inorder to achieve convenient reaction rates, it is preferred to run theprocess from about 0° C. to about 130° C., preferably about 15° C. toabout 50° C., and more preferably about 20° C. to about 30° C. Thereaction may be run neat or in a solvent, but a solvent is preferred.Suitable solvents are polar aprotic solvents that don't react with theingredients or products, such methylene chloride. The solvent should notcoordinate or otherwise substantially react with the Lewis acid. Thereaction may be run in any vessel not affected by the reactants orproducts, such as glass.

When a Lewis acid is used, is it preferred to exclude water and oxygen,since these may react with the starting materials or products. Smallamounts of water or oxygen may be tolerated, but use up some of thereagents. It is convenient to run the reaction under an inertatmosphere, such as nitrogen or argon. Vigorous agitation is preferredto assure mixing of the reactants. The product may be isolated bydistillation after washing with water and neutralizing any residualinorganic acid, or if high boiling, by evaporation of solvent andbyproducts after washing with water and neutralizing.

The products of the above process are useful as catalysts for increasingthe molecular weight of polyamides, as described in U.S. Pat. No.4,912,175, which is incorporated herein.

In another aspect, this invention concerns a compound of the formula##STR7## which is made by the above process using a silane wherein n is3, and more than one mole, and preferably about 3 moles, of silane permole of vinylpyridine or phosphorous compound is used. It is alsopreferred if each R² is independently an alkyl group or phenyl, morepreferred if each R² is a normal alkyl group containing up to 4 carbonatoms or phenyl, and most preferred if R² is methyl. These preferencesalso hold for the process in which these compounds are used as catalystsfor increasing the molecular weight of polyamides. Similar processes forincreasing the molecular weight of polyamides are known to those skilledin the art, for example as described in U.S. Pat. No. 4,912,175, at col.4, line 51 to col. 5, line 6, and the Examples therein. The generalprocedures described in U.S. Pat. No. 4,912,175 may be followed with thepresent compound to increase the molecular weight of a polyamide.

EXAMPLE Example 1

In a nitrogen-filled drybox, 0.11 g (1.05 mmol) of 2-vinylpyridine and0.14 g (1.01 mmol) diethylphosphite were combined in 5 mL of CD₂ Cl₁₂and then separated into 5 equal portions. One portion was used as thecontrol; one portion ("A") was treated with 0.010 g (0.09 mmol) SiMe₃Cl; one portion ("B") was treated with 0.022 g (0.10 mmol) SiMe₃ O₃ SCF₃; one portion ("C") was treated with 0.015 g (0.10 mmol) SiMe₃ Br; andone portion ("D") was treated with 0.010 g (0.09 mmol) SiMe₃ Cl and0.010 g (0.10 mmol) NEt₃. ¹ H NMR spectra of the 5 samples were recordedapproximately 12 hours after preparation. The control sample had onlyunreacted starting materials; A had mostly unreacted starting materialsbut observable amounts (ca. 20%) ofdiethyl-2-(2-pyridyl)ethylphosphonate ("product") (NMR parameters as inExample 9), together with SiMe₃ signals; B and C both had essentiallycomplete conversion of starting materials into compounds havingmethylene ¹ H NMR signals analogous to those of product, together withSiMe₃ signals; D had no observable amounts of product. The NMR spectrumof sample A was recorded again after ca. 24 additional hours, revealingthe formation of additional amounts of product.

Example 2

In a nitrogen-filled drybox, 0.558 g (4.04 mmol) diethylphosphite and0.425 g (4.04 mmol) 2-vinylpyridine were combined without additionalsolvent and treated with 0.020 g (0.09 mmol) SiMe₃ O₃ SCF₃. Smallsamples of this mixture were withdrawn after 5 and 45 minutes, dilutedwith CD₂ Cl₂, and used for ¹ H NMR analysis. Nodiethyl-2-(2-pyridyl)ethylphosphonate ("product") was observed in eithersample. An additional 0.050 g (0.22 mmol) SiMe₃ O₃ SCF₃ was added to themixture; small samples were withdrawn 15, 60, and 100 minutes after thisaddition, diluted with CD₂ Cl₂ and used for ¹ H NMR analysis. Thesesamples showed progressively increasing conversion of the startingmaterials to product, and the conversion was essentially complete (>90%)in the 100-minute sample.

It is believed that the lack of observable reaction following theinitial addition of 0.020 g SiMe₃ O₃ SCF₃ is the result of traces ofmoisture (H₂ O) in the starting materials. Presumably there was enoughmoisture present to deactivate the initial 0.020 g of SiMe₃ O₃ SCF₃ butnot enough to deactivate the additional 0.050 g.

Example 3

In a nitrogen-filled drybox 1.38 g (9.99 mmol) diethylphosphite and 1.05g (9.99 mmol) 2-vinylpyridine were combined without additional solvent,and treated with 0.22 g (2.02 mmol) SiMe₃ Cl. Small samples of thismixture were withdrawn after 38, 70, and 115 minutes, diluted with CD₂Cl₂, and used for ¹ H NMR analysis. A fourth sample was taken from themixture after ca. 48 hours. ¹ H NMR analysis confirmed the appearance ofprogressively increasing amounts ofdiethyl-2-(2-pyridyl)ethylphosphonate ("product") with the conversion ofstarting materials to product being essentially complete (>90%) after 48hours.

Example 4

In a nitrogen-filled drybox 1.38 g (9.99 mmol) diethylphosphite and 1.05g (9.99 mmol) 2-vinylpyridine were combined without additional solvent,treated with 0.20 g (1.84 mmmol) SiMe₃ Cl, and stirred at roomtemperature. Small samples were withdrawn after 10, 40, 70, 100, and 130min, diluted with CD₂ Cl₂, and kept cold (between 0 and -78 deg C) untilanalyzed by ¹ H NMR. A second mixture of diethylphosphite (1.38 g, 9.99mmol) and 2-vinylpyridine (1.05 g, 9.99 mmol) was treated with 0.50 g(4.60 mmol) SiMe₃ Cl and sampled identically. Results of NMR analysisare tabulated below.

In the reaction using 0.50 g SiMe₃ Cl it was observed that a precipitateformed very soon after mixing the reagents. In Example 5 it was shownthat similar mixtures of 2-vinylpyridine, diethylphosphite, and SiMe₃ Clprecipitate a white solid whose ¹ H NMR spectrum is consistent with thatexpected for 2-vinylpyridine hydrochloride.

                  TABLE                                                           ______________________________________                                        time (min) (x.sup.a, 0.20 g SiMe.sub.3 Cl)                                                             (x.sup.a, 0.50 g SiMe.sub.3 Cl)                      ______________________________________                                         10        0.15          0.20                                                  40        0.47          0.62                                                  70        0.62          0.75                                                 100        0.71          0.82                                                 130        0.76          0.87                                                 ______________________________________                                         .sup.a Fraction of starting materials converted to diethyl                    2(2-pyridyl)ethylphosphonate.                                            

Example 5

In a nitrogen-filled drybox, 1.38 g (9.99 mmol) diethylphosphite, 1.05 g(9.99 mmol) 2-vinylpyridine, and 1.08 g (9.94 mmol) SiMe₃ Cl werecombined without additional solvent. A white precipitate formedimmediately and was isolated (0.15 g). The solution was cooled to -30deg C whereupon additional amounts of precipitate formed. A small sampleof the liquid was withdrawn and analyzed by ¹ H and ³¹ P NMR (CD₂ Cl₂solution), revealing signals appropriate for P(OSiMe₃)(OEt)₂ and smalleramounts of 2-vinylpyridine and diethyl-2-(2-pyridyl)ethylphosphonate. ¹H NMR analysis of the precipitate (CD₂ Cl₂ solution) revealed signalsappropriate for 2-vinylpyridine hydrochloride.

Example 6

In a nitrogen-filled drybox, 0.049 g (0.23 mmol) of crudeP(OSiMe₃)(OEt)₂ (prepared from trimethylsilyimidazole anddiethylphosphite) and 0.030 g (0.29 mmol) 2-vinylpyridine were combinedin 2 mL CD₂ Cl₂, and separated into two portions. One portion wasanalyzed by ¹ H NMR with no further additions; the other portion wastreated with 0.011 g (0.07 mmol) trifluoromethanesulfonicacid andanalyzed by ¹ H NMR. In each case the analysis was complete within 15min of mixing. The first portion had no discernable amounts ofdiethyl-2-(2'-pyridyl)ethylphosphonate ("product") and only unreactedstarting reagents were identified; the second portion had essentiallycomplete conversion of phosphite reagents to product and only a smallexcess of 2-vinylpyridine remained.

In a nitrogen-filled drybox 0.080 g (0.56 mmol) crude 2-vinylpyridinehydrochloride (prepared as in Example 5) and 0.092 g (0.55 mmol) P(OEt)₃were combined in 1 mL CD₂ Cl₂. ¹ H NMR analysis (within 24 hrs) revealedessentially complete loss of 2-vinylpyridine and conversion to product.

Example 7

The trimethylsilyl ester of phosphorus acid was prepared separately bycombining 0.40 g (4.88 mmol) phosphorus acid, 1.05 g (10.38 mmol)triethylamine, and 1.02 g (9.39mmol) SiMe₃ Cl in 10 mL tetrahydrofuran,filtering the triethylamine-hydrochloride after 3 days, and evaporatingthe solution to an oily residue having a ¹ H NMR spectrum appropriatefor HP(O)(OSiMe₃)₂ (SiMe₃, 0.3 ppm; HP, 5.7 and 8.0 ppm, in CD₂ Cl₂). Amixture of 0.44 g (1.94 mmol) of this material, 0.21 g (2.00 mmol)2-vinylpyridine, 0.07 g (0.64 mmol) SiMe₃ Cl, and ca. 2 mL CH₂ Cl₂ wasprepared and filtered, and 0.02 g (0.18 mmol) additional SiMe₃ Cl wasadded to the solution. ¹ H NMR analysis after ca. 24 hours revealedlittle if any coupling product. An additional 0.09 g (0.83 mmol) SiMe₃Cl was added to the solution; ¹ H NMR analysis after an additional ca.24 hours revealed essentially complete conversion to the couplingproduct, bis(trimethylsilyl)-2-(2-pyridyl)ethylphosphonate.

Example 8

In a nitrogen-filled drybox, 0.44 g (4.18 mmol) of 2-vinylpyridine and0.56 g (4.05 mmol) of diethylphosphite were combined in 4 mL CD₂ Cl₂. Toone mL of this solution was added 0.036 g (0.19 mmol) TiCl₄ ; to anothermL of the solution was added 0.013 g (0.10 mmol) AlCl₃ ; to another mLof the solution was added 0.026 g (0.10 mmol) SnCl₄. ¹ H NMR spectra,recorded after ca. 24 hr, revealed signals appropriate fordiethyl-2-(2-pyridyl)ethylphosphonate in each sample. Approximateconversions were >50% in the sample containing TiCl₄ and approx.30%(+/-10%) in the samples containing AlCl₃ and SnCl₄.

Example 9

A dry r. b. flask under a positive pressure of nitrogen was loaded with1500 ml of 2-vinylpyridine (13.9 moles) and 1780 ml of diethylphosphite(13.8 moles). Over the next hour 365 ml of trimethylchlorosilane (2.88moles) were added slowly dropwise with mechanical stirring, giving aslow exotherm from room temperature to 50° C. Ice bath cooling was firstneeded about 2/3 into the trimethylchlorosilane addition, and then wasapplied as needed to maintain the reaction mixture between 35° and 50°C. The exotherm was apparent for nearly 3 hours after completion of thetrimethylchlorosilane addition. The reaction mixture was stirredovernight at room temperature.

Volatiles were pulled off the reaction mixture using a vacuum pumpprotected by a dry ice acetone trap and then two liquid nitrogen trapsin series. The dry ice trap collected 130 g of fluid and the firstliquid nitrogen trap 300 g. Four product fractions were collected byslow vacuum distillation using a Vigreux column.

    ______________________________________                                                Pressure Boiling           Oil                                        Fraction                                                                              mm       Pt.         Weight                                                                              Bath                                       ______________________________________                                        #1      .sup. 1-0.8                                                                            146-143° C.                                                                        461.1 g                                                                             194-197° C.                         #2      0.8-0.6  143-141° C.                                                                        944.6 g                                                                             191° C.                             #3      0.6-0.5  141-136° C.                                                                        997.2 g                                                                             191° C.                             #4      0.5-0.8  136-141° C.                                                                        414.3 g                                                                             197° C.                             ______________________________________                                    

Note: one must wait several hours for the vacuum to catch hold and nottry to force distillation by raising bath temperature. The fractionsranged in color from green to yellow and orange with color deepening onstanding. When done on ordinary laboratory scale the product can benearly white and stable in color. Proton NMR spectra of all four productfractions were as expected except for up to 0.2H of extra (CH₃)₃ Siprotons as singlets in the 0 to 0.4 ppm range: 6H 1:2:1 triplet @ 1.3ppm, 2H multiplet @ 2.2 ppm, 2H multiplet @ 3.1 ppm, 4H multiplet @ 4.1ppm, and 4 aromatic H @ 7.1, 7.2, 7.6 and 8.5 ppm.

The total yield of diethyl 2-(2-pyridyl)ethylphosphonate was 2817g(84%). Diethyl 2-(2-pyridyl)ethylphosphonate is a severe eye irritant inrabbits, and eye damage is increased by washing with water.

Example 10

A dry r. b. flask was loaded with 108 ml of 2-vinylpyridine (1 mole) and92 ml of dimethylphosphite (1 mole) under nitrogen. Dropwise addition of25 ml of dichlorodimethylsilane (0.21 mole) gave exothermic reaction to86° C. even with ice bath cooling. Once the exotherm subsided thereaction mixture was fitted for vacuum distillation. A possible exothermwas noted around 98° C. The distillation was shut down, the trapscleaned, and distillation recommenced giving 100 g dimethyl2-(2-pyridyl)ethylphosphonate b₀.2 =131°-146° C. as a yellow fluid.Proton NMR in CDCl₃ /TMS showed a 2H multiplet at 2.3 ppm, a 2Hmultiplet at 3.1 ppm, a 6.5 H 1:1 doublet at 3.7 ppm, and 4.5 aromatic Has multiplets between 7.1 and 8.6 ppm.

Example 11

A dry r. b. flask was loaded with 108 ml of 4-vinylpyridine (1 mole) and129 ml of diethylphosphite (1 mole) under nitrogen. Dropwise addition of25 ml of trimethylchlorosilane (0.2 mole) gave exothermic reaction to53° C. with intermittent ice bath cooling. Once the exotherm subsidedthe reaction mixture was fitted for vacuum distillation. A possibleexotherm was noted during distillation with deposition of solids in thelines. The distillation was shut down, the traps cleaned, anddistillation recommenced giving 133 g diethyl2-(4-pyridyl)ethylphosphonate b₀.2 =129°-134° C. as a greenish fluidthat turned light yellow on standing. Proton NMR in CDCl₃ /TMS showed a6H absorption at 1.3 ppm, 1.9H quintet at 2.1 ppm, 2H multiplet at 2.9ppm, 4.2H triplet at 4.1 ppm, 2.1H 1:1 doublet at 7.2 ppm, and a 2.1Hsinglet at 8.5 ppm.

Example 12

A dry flask was loaded with 10.8 ml of 2-vinylpyridine (0.1 mole) and12.9 ml of diethylphosphite (0.1 mole). Addition of 1 ml of silicontetrachloride caused the reaction mixture to momentarily gel andexotherm to 136° C. After another 13 minutes the reaction mixture hadcooled to 68° C. and another 1.5 ml of silicon tetrachloride were added(0.022 moles total silicon tetrachloride) with stirring causing furtherthickening and solids formation. Thirty-seven minutes into the run aproton NMR sample was taken. The NMR spectrum taken several hours laterfound ˜92% conversion to diethyl 2-(2-pyridyl)ethylphosphonate in whichsome of the ethyl groups had been replaced by silicon.

When 0.3 ml of silicon tetrachloride (0.0026 mole) was used the reactionmixture exothermed only to 38° C. and NMR found 35% conversion todiethyl 2-(2-pyridyl)ethylphoshonate after ˜5 hours.

Example 13

A dry r. b. flask under a positive pressure of nitrogen was loaded with54 ml of freshly distilled 2-vinylpyridine (0.5 mole) containing ˜0.1 gof hydroquinone and 64 ml of diethylphosphite (0.5 mole). Over the next18 minutes 60 ml trimethylchlorosilane were added slowly dropwise withmagnetic stirring. Occasional ice bath cooling was applied as needed tocontrol temperature between 30° and 50° C. After another 20 minutes anadditional 130 ml of trimethylchlorosilane were added dropwise (1.5moles chlorotrimethylmethylsilane total) and the reaction mixturestirred overnight at room temperature. The reaction mixture, 226 g of apale yellow solution with a white precipitate, was loaded into astainless steel bomb and heated for 16 hours at 120° C., developing amaximum pressure of 110 psi. The resulting hazy, red solution wasdistilled first at atmospheric pressure (to a pot temperature of 100°C., weight 168 g) and then under vacuum, taking a major cut at 0.1 mmfrom 100° to 133° C., 118.7 g. Assuming this cut to be purebis(trimethylsilyl) 2-(2-pyridyl)ethylphosphonate, the yield was 72%.Proton NMR in CDCl₃ /TMS showed a 16.5 H singlet @ 0.9 ppm. a 2.0 Hmultiplet @ 2.2 ppm, a 2.0 H multiplet @ 3.1 ppm, 2.0 H as twooverlapping peaks @ 7.2 ppm, a 1.1 H triplet @ 7.6 ppm, and a 1.1 Hdoublet 8.7 ppm, in accord with the assumed structure.

A dropping funnel was loaded with 30 g of bis(trimethylsilyl)2-(2'-pyridyl)ethylphosphonate. About 2 ml were added dropwise to 585 mlof acetone and 15 ml of water with vigorous mechanical stirring, givinga hazy solution. After 12 minutes the original haze developed into solidprecipitate and the remaining bis(trimethylsilyl)2-(2'-pyridyl)ethylphosphonate was added dropwise at ˜2 ml/minute overthe next 15 minutes. The slurry was stirred another 5 minutes and vacuumfiltered. Washing with 100 ml of acetone and drying overnight undervacuum, gave 16.0 g of white solid mp=153°-155° C. The yield of2-(2-pyridyl)ethylphosphonic acid was 94% starting frombis(trimethylsilyl) 2-(2-pyridyl)ethylphosphonate or 67% starting from2-vinylpyridine.

Example 14

In a nitrogen-filled drybox, 2.14 g (20 mmol) 2-vinylpyridine and 3.32 g(20 mmol) triethylphosphite were combined in 4.54 g methylene chloride.Separate samples of this solution, each 1.0 g (2.0 mmol 2-vinylpyridine,2.0 mmol triethylphosphite), were treated with the following acids:

(a) trifluoromethanesulfonic acid, 0.30 g (2.0 mmol);

(b) trifluoroacetic acid, 0.22 g (2.0 mmol);

(c) phosphorus acid, 0.16 g (2.0 mmol);

(d) formic acid, 0.10 g (2.0 mmol);

(e) benzoic acid, 0.25 g (2.0 mmol); and

(f) acetic acid, 0.12 g (2.0 mmol).

Each mixture was stirred for 4 hours at room temperature, then analyzedby ¹ H NMR (CD₂ Cl₂ solution). (a), (b) and (c) had essentially complete(>90%) conversion to diethyl-2-(2-pyridyl)ethylphosphonate ("product");(d) had approximately 57% conversion to product; (e) had approximately21% conversion to product; and (f) had approximately 23% conversion toproduct.

Example 15

In a nitrogen-filled drybox, 1.05 g (10 mmol) 2-vinylpyridine and 1.38 g(10 mmol) diethylphosphite were combined. Half of this solution wastreated with 0.24 g (1.0 mmol) of triphenylboron and the resulting whitesuspension was stirred at room temperature. After ca. 16 hours a portionof the suspension was analyzed by ¹ H NMR (CD₂ Cl₂ solution), revealingapproximately 62% conversion to diethyl 2-(2-pyridyl)ethylphosphonate("product"). After an additional 24 hours a second portion of thesuspension was analyzed similarly, revealing approximately 76%conversion to product.

Although preferred embodiments of the invention have been describedhereinabove, it is to be understood that there is no intention to limitthe invention to such embodiments, that it is to be understood thatmodifications and variations may be made thereto, and that the inventionis defined by the appended claims.

What is claimed is:
 1. A catalytic process for increasing the molecularweight of a polyamide comprising heating a polyamide in the presence ofa compound of the formula ##STR8## wherein each R² is independentlyhydrocarbyl or substituted hydrocarbyl.
 2. The process as recited inclaim 1 wherein the polyamide is heated in the presence of said compoundof the formula ##STR9##
 3. The process as recited in claim 1 whereineach R² is independently an alkyl group or phenyl.
 4. The process asrecited in claim 3 wherein each R² is independently a normal alkyl groupcontaining up to four carbon atoms or phenyl.
 5. The process as recitedin claim 4 wherein said R² is methyl.
 6. The process as recited in claim2 wherein each R² is independently a normal alkyl group containing up tofour carbon atoms or phenyl.
 7. The process as recited in claim 6wherein said R² is methyl.